Device for holding workpieces for machining operations, especially for sewing

ABSTRACT

The present invention pertains to a device for producing three-dimensional casings, which, for holding blanks that are preferably made of materials having a low bending strength, has a carrier body, on which the blank can be mounted in a detachable manner, wherein the carrier body has at least one holding unit with a holding element, whose contact area can be transferred from a resting position situated within the carrier body into a contact position situated outside the carrier body.

FIELD OF THE INVENTION

The present invention pertains to a device for holding at least oneblank or workpiece, made of a material preferably having a low bendingstrength, in a predetermined position during a machining operation,especially during a sewing operation, for the production of athree-dimensional casing. The device has a carrier body, which isprovided with at least one contact surface and essentially correspondsto the shape of the casing to be produced. The blank can be mounted onthe contact surface in a detachable manner, and the device is providedwith at least one holding unit, which holds the blank on the contactsurface during the machining operation.

BACKGROUND OF THE INVENTION

In order to machine blanks made of a material having low bendingstrength into three-dimensional casings with automated productiondevices, it is possible to mount the blanks on a carrier body, whichessentially has the shape of the casing to be produced. In this case,the blanks are arranged at an angle to one another such that their edgeareas at least partially overlap. Subsequently, a suitable tool, e.g., asewing machine arranged on an arm of a manipulator, moves along theoverlapping area, by means of which the two blanks are connected. Alarge field of application exists for this, e.g., the sewing of textilematerials or leather. Since the sewing machines of such automated sewingsystems move along predetermined paths, it is necessary for the blanksto be arranged exactly at the positions provided for this during thesewing operation.

However, based on the low-bending-strength properties of thesematerials, it has proved to be difficult to achieve and maintain thispositioning for the duration of the machining operation. Therefore,corresponding devices exist in the state of the art in order toguarantee this maintaining of position. Thus, each feeding device isfitted with a blank and together with this blank is arranged on acarrier body in a device that has become known from German Patent DE-PS42 25 008. After the feeding device has been removed again, its holdingplates remain on the blank. The metallic holding plates then press theblank, which is located between them and the carrier body, onto thecorresponding contact surface of the carrier body by means of a magnetof same. In order to hold the blank securely, the pressing surfaces ofthe holding plates are only slightly smaller than the blank, so that theedge zone of this blank to be machined protrudes against these pressingsurfaces. Since the holding plates also lie on the side of the blankopposite the carrier body during the sewing, the blank is not readilyaccessible. The movement of the sewing arm of a sewing machine musttherefore be adapted to the arrangement of the holding plate, which,above all, is felt to be a disadvantage if the blank is to be, e.g.,also embroidered. It is likewise not satisfactory that the holdingplates must be removed again after the sewing operation and be fed againto the carrier body after the casing has been removed from same. Inaddition, the fixing of the blanks by means of holding plates leads tothe fact that the feeding device, since it must accommodate a holdingplate in addition to the particular blank, is structurally relativelycomplicated. Furthermore, this manner of fixing the blanks is relativelytime-consuming, since the holding plates must be handled outside of theactual sewing operation, whereby the time needed for a machining cycleof a casing is relatively long.

SUMMARY AND OBJECTS OF THE INVENTION

The object of the present invention is to provide a device of the typedescribed in the introduction, by means of which a blank or workpiececan be held securely during a machining operation, without having thedescribed disadvantages.

This object is attained with a device where each holding unit hasholding elements arranged in a recess of the carrier body. These holdingelements can be transferred from a resting position situated within thecarrier body to a contact position, in which their contact sections arelocated outside the carrier body.

In a preferred embodiment, the holding elements are each able to beacted upon by a pressure medium and are provided with a spring element.To achieve an especially rapid transfer of the holding elements into thecontact position, it is thus advantageous that the holding elementtransfers to the resting position by means of being acted upon by apressure medium, and it also remains there for the duration of thepressurization. It is thereby guaranteed that the stay of the holdingelements in the contact position is independent of a possible drop inpressure.

A further advantage of this embodiment of the present invention is thatenergy must only be supplied for the transfer of the holding elementsfrom the contact position into the resting position, and the holdingelements remain in the working position by means of the action of thespring elements. However, in other embodiments of the present invention,the holding elements may be designed such that they are moved into thefinal positions, e.g., by means of electric or magnetic energy.

Moreover, the holding elements are preferably able to be transferredfrom the resting position into the contact position by means of amovement, which is essentially parallel to their longitudinal axis. Thislikewise contributes to a simple structural design, since, in this case,the recesses may be produced by cylindrical holes, on the one hand, andrectilinear movements can be carried out in a structurally relativelysimple manner, on the other hand.

In another preferred embodiment of the present invention, it is possiblefor the holding elements to have needles, wherein the contact sectionsare formed by their tips. Thus, especially flexible materials are ableto be fixed securely. Moreover, in the case of these types of materials,needles have the advantage that they exhibit only very little wear, andthus, longer service lives are possible.

In order to fix, e.g., leather or foil blanks during a machiningoperation while avoiding damage caused by needle punctures, it may beadvantageous for the holding units either to have a suction device thatgenerates a vacuum or to be provided with a push rod, which brings anadhesive tape, which is to be moved by it, into contact with the blank.Embodiments of the present invention, in which combinations of suctiondevice, push rod with adhesive tape and/or needles may be provided asholding elements, are, of course, also possible.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a top view of a device integrated into a sewing system;

FIG. 2 is a top view of a contact surface of a carrier body;

FIG. 3 is a section of the sectional view along the line III--III ofFIG. 2; and

FIG. 4 is a view corresponding to FIG. 3 of a second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, the present invention includes a device forholding workpieces, e.g., blanks made of materials preferably having lowbending strength that are used to produce three-dimensional casings. Thedevice is integrated into an automated sewing system and is arranged onan arm mount 2 that is rotatable about an axis 1 in the clockwisedirection, as shown in FIG. 1 to illustrate a possible application ofthe present invention. The device has three carrier bodies 3, 4 and 5.The outer shape of the carrier bodies substantially or essentiallycorresponds to the shape that the finished casings are to have. A sewingsystem to be used in this context is described in detail in DE-PS 42 25008, as mentioned in the introduction.

In FIG. 1, the carrier body 3 is in a position, in which it is alreadyfitted with blanks 6. This position is the sewing position. The carrierbody 4, which has yet to be fitted with blanks, is in a fitting positionand will be fitted there by means of a feeding device 7. In contrast,the carrier body 5 is positioned such that the blanks, which havealready been sewn together, are able to be removed from it. All thecarrier bodies 3, 4, 5 are provided for holding the blanks 6 each withone or more contact surfaces 8, 8', 8".

The contact surface 8 of the carrier body 4 shown in FIG. 2 has outletopenings 11, whose central points are arranged on an imaginary line 12,which is at a constant distance from the boundary edge 13 of the contactsurface 8. In FIG. 2, the outlet openings 11 have the shape of ellipses.The outlet openings 11 are the openings of cylindrical recesses 10,which are provided in the carrier body 4 and are formed by correspondingholes. The contact surfaces 8 may be curved as is apparent from FIG. 3.

An opening 14, which serves as a feed line 15 for a pressure medium,e.g., compressed air, opens into the recesses 10. The second contactsurface 8' of this carrier body, which runs at an angle to the firstcontact surface 8, is likewise provided with recesses 10, which are alsosupplied with the pressure medium via a feed line 15. All feed lines 15may be connected to a source of compressed air shared by all carrierbodies.

A holding unit 16 is arranged in the recess 10, as shown in FIG. 3. Thelongitudinal axis of the holding unit 16, which coincides with thelongitudinal axis 17 of the recess 10, forms an acute angle, amountingto approximately 30 degrees in the exemplary embodiment shown, with atangent 18 to the contact surface 8. The holding unit 16 has a threadedsleeve 24, which is hermetically screwed into an internal thread of therecess 10. On its end facing the contact surface 8, the threaded sleeve24 has an opening 25 for the passage of a holding element 26, which isformed by a needle 27 provided with a tip 28. The overall length of theneedle 27 is shorter than the length of the opening 10, such that thetip 28 of the needle 27 is in its resting position within the carrierbody. On the end of the needle 27 facing away from the tip 28, theneedle is provided with a cylindrical extension 29, which is guidedlengthwise within the recess 10. A spring element 30, which is designedas a compression spring and which controls the needle 27 towards thecontact surface 8, is arranged between the area of the recess 10 and theoutside of the extension 29.

The threaded sleeve 24, in its area situated between the front end ofthe opening 25 and the extension 29, has an opening 31, which isutilized for the passage of the pressure medium flowing out of theopening 14.

If the carrier body 4 is now to be fitted with blanks 6, the carrierbody is moved to a feeding station. Then these blanks 6 are broughtforward to the contact surfaces 8 by means of the feeding device 7 andheld initially at the contact surfaces by the feeding device. Theholding units 16 are acted upon with pressure medium via the sharedpressure line 15, so that the tips 28 of the needles 27 are in theirresting position within the recesses 10. The pressure line 15 isdeaerated or unpressurized, so that, with the spring element 30 nowbeing released, the needles 27 move out of the carrier body onto theblank and penetrate this blank completely or partially. Since theneedles 27 are arranged uniformly distributed along the edge area ofeach of the contact surfaces 8, they exert, on the basis of theirsloping position, a relatively low tension on each blank 6 in the nowreached contact position, and they hold this blank on the respectivecontact surface 8 after the feeding device 7 returns to its initialposition. The carrier body 4 can now be brought into the machiningstation or sewing position, which has since been taken by the carrierbody 3, and the blanks 6 can be sewn together in any manner.

After the sewing operation, the carrier body 4 is again further rotatedby a fractional pitch and is then in the removal position or station, inwhich the carrier body 5 was initially. The casing formed may now beremoved from the carrier body 4. For this purpose, the pressure line 15is acted upon, by means of which compressed air is likewise supplied tothe holding units 16. The pressure overcoming the force of the springelement 30 moves the holding units 16 and thus the needles 27 with theirtips 28 from their contact position situated outside the carrier bodyinto the resting position situated within the carrier body, wherein theywithdraw from the blank 6 and release this blank.

In the further embodiment of the present invention shown in FIG. 4, thecarrier bodies 3, 4 and 5 each have, on their respective contactsurfaces 8, 8' a stripper plate 32, 32' which is attached to therespective contact surfaces 8, 8'. Each of the stripper plates isprovided with holes 33, whose center points are each on the longitudinalaxis 17 of the recess 10. The diameter of the holes 33, which form theactual outlet openings 11 for the needles 27 in this case, areconsiderably smaller than the diameter 10 of the recess 10 and areadjusted to the needles 27, such that the needles 27 cannot draw theblank into the recess 10 during their movement from their contactposition into the resting position. On the contrary, the blank isstripped from the needles during their return movement from therespective stripper plate 32, 32'.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

I claim:
 1. A device for combining a plurality of flat workpieces into athree dimensional final shape, the device comprising:a carrier body witha plurality of contact surfaces forming a shape substantially similar tothe three dimensional final shape of the workpieces, each of saidcontact surfaces defining a plurality of recesses; a plurality ofholding means for holding each of the workpieces against one of saidcontact surfaces and in conformance with three dimensional final shape,each of said holding means being positioned in one of said recesses,said each holding means including a holding element movably positionedin a respective said recess, said holding element including a contactsection for piercing the workpieces, said holding element being movablebetween a resting position where said holding element is positionedwithin said carrier body and a contact position where said contactsection of said holding element is positioned outside said carrier body.2. A device in accordance with claim 1, wherein:said holding elementseach have a longitudinal axis, and each said holding element is movablebetween said resting position and said contact position along adirection substantially parallel to a respective said longitudinal axis.3. A device in accordance with claim 1, wherein:said holding element isa needle and said contact section includes a tip insertable into theworkpieces at an angle to hold the workpieces against the controlsurfaces.
 4. A device in accordance with claim 1, wherein:said holdingelements each have a longitudinal axis, and each longitudinal axis formsan acute angle with a tangent to a respective said contact surface.
 5. Adevice in accordance with claim 1, wherein:said plurality of holdingmeans are operable by a pressure medium.
 6. A device in accordance withclaim 5, wherein:said plurality of holding means are connected to ashared pressure line.
 7. A device in accordance with claim 1,wherein:each of said plurality of holding means includes a springelement.
 8. A device in accordance with claim 5, wherein:pressure fromsaid pressure medium forces said holding element into said restingposition; each of said plurality of holding means includes a springelement moving said holding element into said contact position in anabsence of pressure from said pressure medium.
 9. A device in accordancewith claim 1, wherein:said carrier body includes a stripper platepartially covering said recesses, said stripper plate defining aplurality of holes for passage of said contact sections.
 10. A device inaccordance with claim 1, wherein:said contact surfaces include aboundary edge, said holding means holding the respective workpiecesagainst the boundary edge; a distance from said boundary edge of saidcontact surfaces to said holding element in said contact position isless than a distance from said edge to said holding element in saidresting position.
 11. A device in accordance with claim 1, wherein:theworkpieces are substantially two-dimensional objects and said contactsurfaces extend in three dimensions, said holding means holds theworkpiece in said three dimensions; said contact section in said contactposition is positioned on an opposite side of a respective said contactsurface from said carrier body; said contact section in said restingposition is positioned on a side of said respective contact surfaceadjacent said carrier body; said holding elements each have alongitudinal axis, and each longitudinal axis forms an acute angle witha tangent to a portion of a respective said contact surface adjacent arespective said recess, said acute angle having an opening in adirection toward an edge of said respective contact surface; saidholding means holds the workpieces at a position for machining of theworkpieces; said carrier body positions said contact surfaces at anglesto one another; the workpieces have a low bending strength.
 12. A devicein accordance with claim 1, wherein:an arm mount includes a plurality ofsaid carrier bodies, said arm mount being movable so that said pluralityof carrier bodies move between a feeding station, a machining stationand a removal station; a feeding means places the workpieces againstsaid contact surfaces at said feeding station; said holding means hassaid holding elements in said resting position prior to the workpiecesbeing placed against said contact surfaces, said holding means has saidholding elements in said contact position after the workpieces areagainst said contact surfaces, said feeding means moving away from acarrier body at said feeding station after said holding means are insaid contact position.
 13. A device in accordance with claim 1,wherein:said each of said contact surfaces with respective said holdingmeans holds edges of the plurality of workpieces adjacent for joining,said holding means of a respective said contact surface being positionedinside of said edges of said workpiece.
 14. A device in accordance withclaim 1, wherein:said each of said contact surfaces with respective saidholding means holding edges of the plurality of workpieces adjacent forjoining, said holding means of a respective said contact surface beingpositioned along a line spaced from said edge by a substantiallyconstant distance.
 15. A device in accordance with claim 1, wherein:saideach of said contact surfaces has a boundary edge, said holding means ofsaid each contact surface holding a respective workpiece against arespective said boundary edge, said holding means of a respective saidcontact surface being positioned inside of said respective boundaryedge.
 16. A device in accordance with claim 1, wherein:said each of saidcontact surfaces has a boundary edge, said holding means of said eachcontact surface holding a respective workpiece against a respective saidboundary edge, said holding means of a respective said contact surfacebeing positioned along a line spaced from said boundary edge by asubstantially constant distance.